Comparison of chlorophyll fluorescence with several other techniques used to assess chilling sensitivity in plants

Abstract

Chilling tolerance in eight taxa was estimated from field and controlled environment observations and compared to tolerance estimated using a variety of techniques. The controlled environment observations suggested that the eight taxa could be ranked from chilling tolerant to chilling sensitive in the order: pea (Pisum sativum L. cv. Greenfeast), Passiflora edulis Sims., Passiflora ligularis Juss. and Passiflora quadrangularis L., pepino (Solanum muricatum L.) cultivars Comeraya, Suma, Miski, and mungbean [Vigna radiata (L.) R. Wilcz]; although the relationship between the passionfruit as a group and the pepinos was unclear.The change in the variable component of chlorophyll fluorescence (FR) with time near 0°C in darkness was the most reliable method of ranking the plants according to relative chilling tolerance. It was also sufficiently sensitive to discriminate clearly between the closely related pepino cultivars. The Passiflora species and pea were not susceptible to short term reductions in FR, with or without a 20 min exposure to light. Exposure to light at temperatures near 0°C emphasised the reductions in FR in the more sensitive species. Pea was the only species capable of recovering a measurable FR after a 60 min exposure to white light.Measurement of electrolyte leakage and ethylene evolution from leaf disks after a low temperature treatment could allow discrimination between closely related varieties, but not between genera. Catalase activity was reduced in all taxa in response to low temperature. However, both initial catalase levels and relative response to dark treatment at 20°C enabled the ranking of plants within the closely related subgroups according to susceptibility to chill injury.No one method clearly distinguished chilling sensitivity over all taxa.